1. Technical Field
The present disclosure relates to semiconductor structures, a light emitting diode, and a method for making the same.
2. Description of Related Art
Semiconductor structures fabricated by gallium nitride for light sources, such as blue, green, and white light sources, have long lifetime, high energy conversion efficiency, and is environmentally friendly. Therefore, the semiconductor structures are widely used as the light sources in large screen color display systems, automotive lighting, traffic lights, multimedia displays, optical communication systems, and so on.
A semiconductor structure used in a standard light emitting diode (LED) includes an N-type semiconductor layer, a P-type semiconductor layer, and an active layer located between the N-type semiconductor layer and the P-type semiconductor layer. In an operation, a positive voltage and a negative voltage are applied respectively to the P-type semiconductor layer and the N-type semiconductor layer. Thus, holes in the P-type semiconductor layer and electrons in the N-type semiconductor layer can enter the active layer and combine with each other to emit visible light, and the visible light is emitted from the semiconductor structure. However, near field evanescent waves emitted from the active layer are internally reflected inside the semiconductor structure, so that a large portion of the light emitted from the active layer remain in the semiconductor structure, thereby degrading the light extraction efficiency of LED.
What is needed, therefore, is to provide a semiconductor structure for solving the problem discussed above.